Objective: To determine the relations between traumatic brain injury (TBI) and several neurologic outcomes 6 months or more after TBI.
Participants: Not applicable.
Design: Systematic review of the published, peer-reviewed literature.
Primary measures: Not applicable.
Results: We identified 75 studies that examined the relations between TBI and neurologic outcomes. Unprovoked seizures are causally related to penetrating TBI as well as to moderate and severe TBI. There was only limited evidence of an association between seizures and mild TBI. Dementia of the Alzheimer's type (DAT) was associated with moderate and severe TBI, but not with mild TBI unless there was loss of consciousness (LOC); the evidence for the latter was limited. Parkinsonism was associated with moderate and severe TBI, but there was only modest evidence of a link with mild TBI without LOC. Dementia pugilistica was associated with professional boxing. There was insufficient evidence to support an association between TBI and both multiple sclerosis and amyotrophic lateral sclerosis. TBI appeared to produce a host of postconcussive symptoms (eg, memory problems, dizziness, and irritability). Moderate and severe TBI were associated with endocrine problems such as hypopituitarism and growth hormone deficiency and possibly with diabetes insipidus. There was only limited evidence of an association between mild TBI and the development of ocular/visual motor deterioration.
Conclusion: TBI is strongly associated with several neurologic disorders 6 months or more after injury. Clinicians caring for TBI patients should monitor them closely for the development of these disorders. While some of these disorders can be treated after they arise (eg, seizures), a greater public health benefit would be achieved by preventing them before they develop. Research efforts to develop therapies aimed at secondary prevention are currently underway.